Area Forecast Discussion
Issued by NWS Medford, OR
Issued by NWS Medford, OR
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139 FXUS66 KMFR 032108 AFDMFR Area Forecast Discussion National Weather Service Medford OR 208 PM PDT Mon Jun 3 2024 .SHORT TERM...Tonight through Wednesday Night...A few light showers continue on opposite sides of the forecast area: along the Coos and Douglas county coasts, and over Modoc county. The showers over Modoc County are the last lingering effects of the departing front, and should diminish and end over the next several hours, while the showers at the coast are a result of onshore flow, and these could continue through tomorrow afternoon. The onshore flow is resulting from the area lying between the broad ridge to our south and a trough to the northwest, and the resulting swift zonal flow that lies in between them. Although the main belt of this flow lies to our north, the southern periphery does and will continue to overlap into Coos and Douglas counties. Not much will change in this regard over the next 24 hours or so, when the ridge will build north, disrupting the flow, and coming into complete control of the weather over our area. The ridge will result in dry and very warm conditions for our area, with inland highs on Wednesday jumping up to 10 to 15 degrees above normal for this time of year. Temperatures will be warm at the coast as well, although not as drastic. Meanwhile, well to our south, a closed low is forecast to take position just to the west of Baja. Working with the ridge, this will begin to push some moisture north through California and the Great Basin, potentially reaching far southeastern Modoc County by Wednesday afternoon and evening. As a result, an isolated thunderstorm is possible, but the most likely result will be some increased cloudiness through Wednesday night. -BPN .LONG TERM...Thursday through Monday, June 6-10, 2024...The hottest weather of the season thus far is expected Thursday and Friday across southwest Oregon and northern California as a strong upper level ridge sets up over the Four Corners. The axis of the upper ridge will extend far to the north all the way into the PacNW and along the coast of British Columbia, Canada. Mid- level temperatures will soar to around 20C Thursday afternoon, then 22-23C on Friday. This supports highs in the 90s for many west side valleys, including Medford, with 80s/low 90s east of the Cascades. While not a widespread record-breaking heat wave, a few records across the area could be challenged. Mount Shasta City could reach or exceed their records for both Thu/Fri (94F in 2013, 92F in 2015, respectively). Klamath Falls is mostly likely to challenge their record on Friday (91F in 1996) as is Alturas (93F in 1996). The peak of the heat is on Friday with inland temperatures averaging 15-20F above normal. Here in Medford, the official forecast is for 98F and the record high is 101F set in 2015. We`ve seen probabilities of >=100F drop a bit during the last few days and they now stand at 29%. Looking at NWS HeatRisk, this level of heat doesn`t really rise to the point of issuing a heat advisory and falls squarely on the orange moderate (2) scale for our west side valley locations. This is likely due to some relief expected during the overnight hours. Still, it will be hot, so folks sensitive to the heat should consider all the potential heat-related impacts and try to stay cool during the peak afternoon heating period (2-6 pm). Although our forecast area will be primarily influenced by the upper ridge supporting dry weather Thu/Fri, there is a weakness in the upper ridge on its NW periphery. This could provide just enough moisture, instability and trigger to initiate some convective development in portions of NorCal and south-central Oregon both Thu/Fri pm/eve. Flow aloft will be from the south to southwest, so convective clouds likely initiate over higher terrain and there is a slight chance (generally <25%) of thunderstorms. This chance exists mostly from the Cascades/Siskiyou mountains south and east. The rest of the area will remain dry. This weekend, a weak upper trough will move across the area allowing temperatures to trend slightly lower, but still remain well above normal. With the upper trough moving through, a slight chance of thunderstorms persists from the Cascades eastward in Oregon, with the best chance on Sunday. It`s also not out of the question that something pops up near the Trinity Alps during this time period, but right now thunder probabilities are fairly low (<15%). Model ensembles and clusters show a majority of members rebuilding the ridge over the area on Monday of next week, potentially persisting through mid next week. This would keep the PacNW in a pattern of above normal warmth. -Spilde && .AVIATION...03/18Z TAFs...Along the coast and just offshore, MVFR conditions are the predominate condition and this is expected to persist through at least the 18z TAF cycle. Some improvement to ceilings could be expected later in the afternoon, but passing showers will still keep MVFR possible. Inland west of the Cascades, VFR ceilings will prevail for the rest of the day, although a stronger shower across Douglas county could briefly bring MVFR back to the Roseburg terminal. Otherwise, we are expecting gusty north-northwest winds to be present this afternoon and continued obscured terrain. East of the Cascades, MVFR ceilings are expected through the TAF period, with the terrain partly obscured. Strong winds gusting above 20 kt are likely in the afternoon, especially over the higher terrain. Peak wind gusts could push towards 30 kts at the Klamath Falls terminal this afternoon and is most likely to occur around 19z or 20z. Some clearing towards a mix of VFR/MVFR conditions are expected in the afternoon. -Miles && .MARINE...Updated 110 PM Monday, June 3, 2024...Moderate south to southwest winds and west swell are expected today, with conditions hazardous to small craft from the combination of swell and wind wave. Another west swell around 10 to 12 ft at 14 to 15 seconds will build into the waters late Tuesday into Wednesday, which will bring advisory level seas to all areas, as well as uncommon surf heights for June of 16-19 feet. Wednesday evening, a thermal trough will return along the coast. Winds are forecast to gust up to 35 kt between Port Orford and Brookings, which could lead to very steep and hazardous seas beyond 5 nm from shore. However, confidence is too low for a Hazardous Seas Watch for Wednesday evening, but confidence is much higher for Thursday. Thursday, very steep, hazardous seas are expected, with a low chance for gales south of Brookings, too. By Thursday, the west swell should diminish to around 6 ft., but when combined with the wind wave, should be enough to maintain advisory seas north of Cape Blanco also. Calmer seas look to be possible Friday into Saturday. -Miles && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Wind Advisory until 5 PM PDT this afternoon for ORZ031. CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory until 5 AM PDT Tuesday for PZZ350-356-370-376. && $$ BPN/MAS/MCB